Help getting to Vall

[zak233]

Hey everyone, I'm attempting to put a lander/rover on Vall and I'm approaching the Jool system but just can't figure out how to do it. I tried just going straight for a Vall encounter, but I come in so fast I just fly right by it unless I can spend like 7,000 delta v to stop. I tried to go around Jool and sort of aerobrake or at least use a gravity slowdown - once I ended up getting caught by Jool and falling into it, the other I got a sort of slingshot orbit and then encounter with Vall but still came in too quick.

I'm just not sure how to go about it...Hopefully these screenshots give you a decent idea of where I'm at

[Vanamonde]

Unless your ship has ungodly amounts of delta-V, you'll need to do a Jool aerobraking at around 118kms. Ideally, it should look something like this, though the chances of Vall being in the right place for an intercept are quite small. Usually I just get close to its orbital height and warp until I get close enough for an intercept.

[PirateAE]

hate to be honest here, but with just 4 KM of DV left, the chances of you getting on vall is near 0, cause the burn to get aero break around jool would almost kill any chance of getting back to Vall. vall dosent have an athmosphere which is all that would save the mission.

[zak233]

So something like this?

Then I tried to get a Vall intercept from there..

[metaphor]

Yeah something like that. You don't actually have to aerobrake, if you want to only use propulsion get your Jool periapsis right above the atmosphere at 140 km, and then burn retrograde around 680 m/s (assuming you're coming from a Kerbin-Jool transfer, might be more or less depending on your transfer orbit). This will move the apoapsis of your orbit to Vall's orbital distance, and it's more precise than aerobraking. Once your apoapsis is at Vall's orbit, you should look at where Vall is in its orbit so you can get an intercept. Do prograde burns at apoapsis to tweak your orbit so that you encounter Vall, might take a couple of orbits. Get your Vall periapsis low to like 30 km before you enter its SoI and burn retrograde at periapsis to get into low orbit. That should take about 950 m/s. Then landing on Vall takes another 900 m/s. So with the 50 m/s needed to get a low Jool periapsis, that's a total delta-v of about 2580 m/s if you use propulsive maneuvers, or 1900 m/s if you use aerobraking. It's hard to get exactly the right altitude to do aerobraking, would need a lot of F5/F9, that's why I included the propulsive option.